Re: More duplicate code, vnode locking question

[Elad Efrat <elad%NetBSD.org@localhost>]

On Thu, Apr 23, 2009 at 12:24 AM, Antti Kantee <pooka%cs.hut.fi@localhost> 
wrote:
> On Wed Apr 22 2009 at 23:45:01 +0300, Elad Efrat wrote:
>> >> Also, it seems that some file-systems call VOP_OPEN() without devvp
>> >> being locked. Compare, for example, ffs_mount() and efs_mount(). Is
>> >> this possible, or am I missing something? :)
>> >
>> > This is a bug.
>>
>> Okay. Unless someone beats me to it, once I'm done with some other stuff
>> I'll go over the file-systems and make a patch to add locking where it's
>> missing (in this regard only! :) and post it.
>>
>> What I have in mind is adding vn_lock() before the VOP_OPEN() call, and
>> adjust error paths to vput() where the vnode is locked and vrele()
>> otherwise. Is this correct?
>
> I already explained why locking it is a bug also.  Why are you replacing
> a bug with a theoretically more severe bug?  Did you disagree with
> my explanation?

First of all, I'm not replacing anything. All I did was bring into the
discussion what was on my mind to fix the bug. Apparently, I
misunderstood you (I phrase things differently when I disagree).

Also, I have two other questions:

  - How does locking devvp violate the locking order of vnodes? (note
    that I'm not suggesting it doesn't)

  - How do we weigh what is a more severe bug? :)

Thanks,

-e.